Plasma surface treatment method and resulting device

ABSTRACT

The present invention provides a method for treating a surface of an object using, for example, a downstream region of a plasma source. The method includes a step of generating a plasma from a gas-C in a plasma source, where the gas-C includes a gas-A and a gas-B. Gas-A is selected from a compound comprising at least a nitrogen bearing compound or an other gas. The other gas is selected from a mixture of an element in group 18 classified in the atomic periodic table. Gas-B includes at least a NH 3  bearing compound. The method also includes a step of injecting a gas-D downstream of the plasma source of the gas-C. The method also includes a step of setting an object (having a surface) downstream of the gas-D injection and downstream of the plasma source. A step of processing the surface of the object by a mixture species generated from the gas-C in the plasma and the gas-D is included. The NH 3  bearing compound in the gas-C includes a NH 3  bearing concentration that is lower than an explosion limit of NH 3 , which is safer than conventional techniques.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Ser. No. 60/078,321 filed Mar.17, 1998, commonly assigned and hereby incorporated by reference for allpurposes.

BACKGROUND OF THE INVENTION

The present invention relates to objects and their manufacture. Moreparticularly, the invention is illustrated in an example using a novelcombination of gases and a downstream plasma surface for selectivelyremoving photoresist materials for substrates used in semiconductorintegrated circuits. Merely by way of example, the invention can beapplied in the manufacture of other substrates such as flat paneldisplays, micro electrical mechanical machines (“MEMS”), sensors,optical devices, and others.

In the manufacture of objects such as integrated circuits, processingsafety and reliability have been quite important. Fabrication ofintegrated circuits generally require numerous processing steps such asetching, deposition, photolithography and others. In thephotolithography process, for example, a photoresist film of material isoften used to form patterns on thin slices of silicon or films that aredeposited on such silicon. After patterning, however, it is necessary toremove the photoresist film from the silicon using a hydrogen bearingcompound. Additionally, hydrogen bearing compounds are used in plasmatreatment of silicon surfaces. In some cases, hydrogen is used toterminate ends of silicon bonds. Hydrogen is also used to remove oxides.Numerous studies have been made in using a hydrogen bearing compound,and in particular a low temperature process using a reductive reactionfrom atomic hydrogen produced by a hydrogen gas molecule gas plasma. Forexample, an object such as a wafer or hard disk has a surface, which isto be processed at a certain area or reactor exposed to high energyspecies such as ions even in the plasma downstream system. This way ofprocessing occurs because lifetime of atomic hydrogen generated in theplasma is often short and can easily recombine into hydrogen moleculesoutside of the plasma discharge area. Thus, the conventional processoften cannot avoid damage caused by high-energy species such as ions andelectrons, decreasing the controllability of processing.

Numerous techniques using hydrogen for processing devices have beenreported. As merely an example, a conventional process for ashingorganic material, which is carbonized by ion implantation, using atomichydrogen in a downstream plasma of hydrogen diluted by nitrogen orargon, has been reported by in a paper by S. Fujimura, H. Yano, J.Konno, T. Takada, and K. Inayoshi: Study on ashing process for removalof ion implanted resist layer, Process Symposium, Dry Process, ProcedureVol. 88-7, Honolulu, Hi., May, 1987 (The Electrochemical Society Inc.Pennington, 1988) pp. 126-133, which is incorporated herein by referenceherein. It also has been reported that a high concentration atomichydrogen is obtained in plasma downstream by the use of mixture ofhydrogen and water vapor as the source gas for the plasma in J. Kikuchi,S. Fujimura, M. Suzuki, and H. Yano, Effects of H₂O on atomic hydrogengeneration in hydrogen plasma, Jpn. J. Appl. Phys., 32, pp. 3120-3124(1993) (“Kikuchi, et al.”), which is incorporated by reference herein.Kikuchi et al. proposes a method to make an environment of a highconcentration of atomic hydrogen at a downstream region where theinfluence of substantially all high energy species such as ions,electrons, and photons generated by plasma discharge can besubstantially ignored.

Moreover, it was discovered that silicon native oxide could beeliminated at low temperature using NF₃ injected downstream of a H₂+H₂Oplasma. This has been reported by J. Kikuchi, M. Iga, H. Ogawa, S.Fujimura, and H. Yano, Native oxide removal on Si surface by NF3-addedhydrogen and water vapor plasma downstream treatment, Jpn. J. Appl.Phys., 33, 2207-2211 (1994). This silicon native oxide removal processwith NF₃-added hydrogen and water vapor plasma downstream treatmentachieved a removal of silicon native oxide at nearly room temperature invacuum environment and formation of hydrogen terminated silicon surface.Thus, the reported process can replace the conventional high temperaturehydrogen gas pre-treatment of silicon epitaxy. J. Kikuchi, M. Nagasaka,S. Fujimura, H. Yano, and Y. Horiike, “Cleaning of Silicon Surface byNF₃-Added Hydrogen and Water-Vapor Plasma Downstream Treatment,” Jpn. J.Appl. Phys., 35, 1022-1026 (1996). Additionally, it was suggested to usethis method for the several applications of a silicon basedsemiconductor-manufacturing process such as cleaning of a contact holeof ULSI devices, J. Kikuchi, M. Suzuki, K. Nagasaka, and S. Fujimura.The silicon native oxide removal with using NF₃-added hydrogen and watervapor plasma downstream treatment 4. Extended Abstracts (The 44th SpringMeeting, 1997); The Japan Society of Applied Physics and RelatedSocieties, 1997, (29p-W6) in Japanese.).

The aforementioned technologies generally required introducing a highconcentration of a hydrogen gas into a plasma. The high concentration ofhydrogen causes an absolute risk of an explosion. Accordingly, ahigh-level safe system has to be prepared for practical use of thistechnology. For example, restrictions of the use of rotary vacuum pumpwith conventional vacuum pump oil should be prepared. A requirement of avacuum load lock system in order to prevent the leaking of hydrogen fromreaction reactor also need be prepared. A further requirement wouldinclude a high volume dilution inert gas system at exhaust pump gas inorder to reduce the concentration of hydrogen lower than its explosionlimit. Moreover, the system would also require a hydrogen gasleak-monitoring system, a fire extinguishing system, and an alarm systemfor the inside of equipment or installed room itself. These safetyrequirements will generally result in high costs to use this technologyand it will become an obstacle to the growth of the technology in theindustry.

From the above, it is seen that an improved technique of fabricating asubstrate in an easy, cost effective, and efficient manner is oftendesirable.

SUMMARY OF THE INVENTION

According to the present invention, a technique including a method anddevice for the manufacture of treating objects is provided. In anexemplary embodiment, the present invention provides a novel techniquefor treating a surface of an object using a plasma treatment apparatus.

In a specific embodiment, the present invention provides a method fortreating a surface of an object using, for example, a downstream regionof a plasma source. The method includes a step of generating a plasmafrom a gas-C in a plasma source, where the gas-C includes a gas-A and agas-B. Gas-A is selected from a compound comprising at least a nitrogenbearing compound or an other gas The other gas is selected from amixture of an element in group 18 classified in the atomic periodictable. Gas-B includes at least a NH₃ bearing compound. The method alsoincludes a step of injecting a gas-D downstream of the plasma source ofthe gas C. The method also includes a step of setting an object (havinga surface) downstream of the gas-D injection and downstream of theplasma source. A step of processing the surface of the object by amixture species generated from the gas-C in the plasma and the gas-D isincluded. The NH₃ bearing compound in the gas-C includes a NH₃ bearingconcentration that is lower than an explosion limit of NH₃, which issafer than conventional techniques.

In a specific embodiment, the present invention provides an apparatusfor processing an object. The apparatus includes a chamber and a plasmadischarge room coupled to the chamber. A susceptor holds the object,i.e., wafer, display, panel. The plasma discharge room is downstreamfrom the chamber. The apparatus also has a first gas supply comprising agas A coupled to the plasma discharge room, where the gas A comprises anitrogen bearing compound. The apparatus also has a second gas supplycomprising a gas B coupled to the plasma discharge room, where the gas Bcomprises an NH₃ bearing compound. A third gas supply with a gas Dcoupled between the plasma discharge room and the chamber also isincluded. The present apparatus does not generally require load locks orthe like, which are often used with conventional hydrogen processingtools.

The present invention achieves these benefits in the context of knownprocess technology. However, a further understanding of the nature andadvantages of the present invention may be realized by reference to thelatter portions of the specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified drawing of a system according to an embodiment ofthe present invention;

FIG. 2 is a simplified cross-sectional view drawing of an apparatusaccording to an embodiment of the present invention;

FIG. 3 shows a concentration of atomic hydrogen in a H₂O+N₂ gas plasmavs. H₂O ratio of total plasma gas flow according to an embodiment of thepresent invention;

FIG. 4 shows a simplified relation between an etching speed of silicondioxide and an atomic hydrogen concentration in a downstream area usingthe system of FIG. 1;

FIG. 5 shows etching depth of SiO₂ as a function of gas flow ratio ofwater-vapor and nitrogen with water-vapor diluted with nitrogen mixedgas plasma due to 500 watt, 2.45 GHz microwave and added NF₃ into downflow section under a pressure 2.0 Torr and a processing time of 3minute;

FIG. 6 shows a dependence of etching depth of SiO₂ on the mixing ratioof water vapor and nitrogen in a surface treatment using equipment shownin FIG. 2, for example; and

FIG. 7 is a simplified cross-sectional view diagram of a barrel typeplasma ashing system according to an embodiment of the presentinvention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

According to the present invention, a technique including a method anddevice for the manufacture of treating objects is provided. In anexemplary embodiment, the present invention provides a novel techniquefor treating a surface of an object using a plasma treatment apparatus.

In a specific embodiment, the invention relates to a surface materialtreatment method with use of the plasma producing atomic hydrogen, forexample. The invention also relates to a surface treatment method usingatomic hydrogen which is produced by a plasma. In an alternativeembodiment, the present invention uses a catalytic action of nitrogen,helium, neon, argon, krypton, xenon and/or radon, as well as otherelements, as a part of a plasma source gas. The invention also uses astep of applying under a downstream plasma method which has features ofbeing substantially free from physical surface damage. In some of theseembodiments, the present invention also reduces or minimizesinappropriate active species for the purpose of treatment, therebyproviding a more efficient and effective process. Accordingly, thepresent invention can provide advantages such as decreased costs andincreased safety in surface treatment of a downstream plasma generatingatomic hydrogen, for example.

For easier reading, we have prepared the following list of items andtheir names, which are shown in the FIGS. for referencing orcross-referencing purposes. These names are merely shown forillustration purposes and should not limit the scope of the claimsherein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives.

1. #1 Gas inlet

2. Microwave guide

3. Microwave cavity

4. #2 Gas inlet

5. Chamber

6. Treatment room

7. Silicon substrate

8. Exhaust

11. Plasma discharge room

12. Gas-A supply unit

13. Gas-B supply unit

14. Fitting

15. Microwave generator

16. Wave guide

17. Microwave cavity

18. Nozzle

19. Gas-D supply unit

20. Fitting

21. O-ring

22. Treatment room

23. Treatment material

24. Treatment stage

25. SiC heater unit

26. Vacuum Exhaust port

27. Loading & Unloading port

28. Inside wall

31. Quartz reaction tube

32 a, 32 b. Electrode

33. RF generator

34. Wafer carrier

35. Wafer

36. Cover

37. Aluminum etch tunnel

Again, the above list of names are merely shown for illustrativepurposes. These names are not intended to limit the scope of the claimsherein.

Before proceeding to the details of the embodiments of the presentinvention, it may be helpful to fully understand some of the additionallimitations with conventional processing techniques. As merely anexample, in an attempt to solve some of the risks associated with theabove hydrogen gas techniques, Japanese Patent published under KOKAIH6-338578, which is based upon the paper above (J. Kikuchi, M. Nagasaka,S. Fujimura, H. Yano, and Y. Horiike, Cleaning of Silicon Surface byNF₃-added Hydrogen and Water-Vapor Plasma Downstream Treatment, Jpn. J.Appl. Phys., 35, 1022-1026 (1996).), describes an alternative technique.It has been suggested that the capability of removing silicon nativeoxide by adding NF₃ gas from the down steam region of hydrogencontaining gas plasma. The definition of “gas containing hydrogen”claimed in item number 1 and 4 in this official patent report, is notclear, however. The paper indicated an achievement of the objectivepurpose due to the reaction of atomic hydrogen and NF₃.

Taking this in a broad sense, this suggests that a silicon native oxidelayer would be removed by injecting NF₃ into the downstream of anyplasma, which is generated with a gas containing hydrogen atoms as itselement and produces atomic hydrogen. Therefore, if the same result ofsurface treatment in quoted paper is achievable with using H₂O moleculeplasma, which is generating atomic hydrogen, issues of safety andeconomical requirement indicated above, is solved. Additionally, watervapor is indicated, to carry a hydrogen atom described in the abovequoted paper.

FIG. 1 shows a plasma down stream process system using a quartz tubesimilar to the FIG. in the official patent report KOKAI H6-338578. Usingthis system, for example, a process for trying to etch silicon thermaloxide set at a down flow region of plasma has been performed under thesefollowing conditions. (Process time 30 minute, Processing pressure 1Torr, 30 sccm H₂O as plasma source gas, 50 watt 2.54 GHz microwave asplasma generating source energy, and 5 sccm NF₃ added from down flowregion of plasma.) A decrease in the thickness of the oxide was notdetected in the measurement by ellipsometry. Additionally, the siliconwafer surface with a native oxide did not turn either from hydrophilicto hydrophobic after the treatment. This meant that the native oxide wasnot removed. The process was tested under different operation conditionswith changing pressure from about 0.5 Torr to about 3.0 Torr andchanging flow rate of 10 sccm H₂O and 10 sccm NF₃. The result showed,however, no evidence of silicon dioxide etching.

The native oxide was not removed even using the equipment shown in FIG.2 and got thicker in size to apply to practical treatment, under thefollowing conditions: 100 sccm H₂O, 100 sccm NF₃, 500 watt 2.54 GHzmicrowave power, processing pressure 1 Torr; and process time 10minutes. The result showed there is no evidence of removing nativesilicon dioxide.

FIG. 3 shows the dependence of a concentration of atomic hydrogen in aH₂O+N₂ gas plasma on an H₂O flow ratio to total gas flow. Theconcentration of atomic hydrogen in the plasma was measured using aactinometry method. Concrete conditions of the actinometry of atomichydrogen are described in J.VAC. Sci. Technol. B, 9, 357-361 (1991). Theresult shows that the highest concentration of atomic hydrogen wasobserved at 100% H₂O and the concentration of atomic hydrogen decreaseswith decreasing in H₂O ratio monotonously.

Above experimental results indicate that an etching reaction of silicondioxide as described in the official patent report KOKAI H6-338578 doesnot occur in the system with a 100% H₂O plasma and NF₃ injection to adownstream region, through atomic hydrogen is surely generated in theplasma. Thus, an altered process with NF₃ injection into the downstreamof an water vapor plasma as the source of atomic hydrogen does not etchsilicon dioxide though the process satisfies the necessary andsufficient condition which is the existence of atomic hydrogen and NF₃and is described in the official patent report KOKAI H6-338578.Therefore, this process could not achieve solving the issues of safetyand economical requirement.

In order to solve the above limitations, the relationship between theetch velocity of silicon dioxide and hydrogen atom concentration indownstream area was investigated with the system shown in FIG. 1.

An experiment has been done as follows.

a) Generating a plasma with H₂O and N₂ mixed gas with a total gas flowof 30 sccm and 2.54 GHz Microwave of 50 watts.

b) Injecting NF₃ of 5 sccm into the downstream of the plasma.

c) Estimating the concentration of atomic hydrogen at 1 Torr by acalorimetry method using a shielded thermocouple, which is covered withquartz except at the tip and inserted into the area where object wouldbe set. The calorimetry method to measure atomic hydrogen flow isdescribed in, for example, “Young C. Kim and Michel Boudart,Recombination of O, N, and H Atoms on Silica: Kinetics and Mechanism,Langmuir, 7, 2999-3005 (1991), and L. Robbin Martin, “Diamond filmgrowth in a flowtube: A Temperature Dependence Study”, J. Appl. Phys.,70, 5667-5674 (1991)”.

d) Heating a certain place of the tube up to 500 degree Celsius betweenthe NF₂ injection point and the point where the object would be set.(Heating increases the reaction rate between atomic hydrogen and NF₃ toincrease etching velocity. As the result, error in measurement inetching depth is reduced or minimized.)

e) measuring etching depth of the samples treated under severaldifferent operation conditions.

A flow rate of each gas is shown in FIG. 4 near by measurement point.Number on the left side of “:” indicates H₂O flow rate and that on theright side of “:” indicates N₂ flow rate. A unit of gas flow is measuredin sccm.

In FIG. 4, the concentration of the hydrogen atom is normalizedappropriately. From FIG. 4, it is clear that silicon dioxide is notetched in the treatment in 1 Torr with H₂O of relatively highconcentration in the H₂O and N₂ mixed gas (from 100% to 33% ) thoughatomic hydrogen exists at the point where the objects have been set.Under the condition of H₂O concentrations lower than 17% (H₂O flow rateis less than 5 sccm), however, silicon dioxide etch was observed and theconcentration of atomic hydrogen was also relatively higher than thatunder the condition with high H₂O mixing ratio.

FIG. 3 shows that the concentration of atomic hydrogen in the plasmaincreases with the mixing ratio of H₂O ratio in the mixed gas, thus theconnection of atomic hydrogen in plasma at the H₂O mixing ratio of 17%is almost 1/20 of that at 100% H₂O.

Moreover, the concentration of atomic hydrogen in the plasma at H₂O of17% where that in the downstream was the highest is about 1/100 ofatomic hydrogen concentration in the plasma at 100% H₂O. On the otherhand, the concentration of hydrogen atom in the downstream at 7% H₂O isalmost 13 times as large as that at 100% H₂O. These results seem to showthat nitrogen generated atomic hydrogen. The disassociation ratio of100% H₂O gas by 2.54 GHz microwave discharge is the order of ten. See L.Brown, J.Phys. Chem., 71, 2429 (1967). Even taking into consideration ofthe difference in plasma conditions, a disassociation ratio of H₂O inthis experiment would still be several percent. If H₂O can carry atomichydrogen toward a down flow region without a decrease in the amount ofatomic hydrogen independently of operating conditions, the concentrationof atomic hydrogen in the downstream would reflect that in the plasma.Thus, the fact that the numerical ratio of atomic hydrogen concentrationat the 7% H₂O to that at the 100% changes from 1/100 to 13 with shift inthe measurement position from the plasma to the downstream is notconvinced, even if nitrogen disassociates water vapor and increases theconcentration of atomic hydrogen.

Consequently, it is a reasonable interpretation that the effect of watervapor on atomic hydrogen transportation reported in the paper written byJ. Kikuchi, S. Fujimura, M. Suzuki, and H. Yano is effective in thecondition with a relatively lower H₂O mixing ratio in plasma source gasand ineffective in the condition with H₂O mixing ratio close to 100%,because hydroxyl radical (OH) and atomic oxygen (O) generated in theplasma quench atomic hydrogen by recombination between them. (When thesmall amount of H₂O was mixed into H₂, OH or O has a higher possibilityto collide with a hydrogen molecule instead of atomic hydrogen, then OHand O abstract a hydrogen atom from hydrogen molecules and generate H₂Oand OH and one free atomic hydrogen is simultaneously produced. In thisresult to be produced is a free hydrogen atom from hydrogen molecule.)Therefore, these experiments result that the carrying mechanism ofatomic hydrogen from plasma to downstream with mixing nitrogen up to bemajority in a N₂+H₂O mixing gas as a plasma source is different fromthat described in the official patent report KOKAI H6-338578 and somespecies with catalysis made in the plasma from the nitrogen moleculeprobably caused the above phenomena that atomic concentration in thedownstream at H₂O mixing of several percent was larger than that at 100%H₂O.

Experimental results in 1 Torr shown in FIG. 4 seems to also show thathigher atomic hydrogen concentration induces larger velocity of silicondioxide etching. For example, however, silicon oxide was etched by 13 Adepth during 5 minutes of treatment under the condition where thetreatment pressure was 2 Torr. The flow rate of water vapor and nitrogenwas 2 and 28 sccm and not etched under the condition where the treatmentpressure was 1 Torr and the flow rate of water vapor and nitrogen was 10and 20 sccm, though the concentration of atomic hydrogen in the formertreatment condition was about 1/8 of that in the latter. In the processperformed using a gas mixed with a small amount of water vapor andnitrogen, therefore, the velocity of silicon dioxide etching caused byNF₃ injection into the downstream is not always in proportion to theconcentration of atomic hydrogen. Taking consideration into the factthat the silicon dioxide etching does not occur depending upon theoperating condition in spite of existence of enough amount of atomichydrogen, this result concludes that silicon dioxide etching in thisH₂O+N₂ process does not mainly based on the effect of atomic hydrogenand NF₃ as shown in the official patent report KOKAI H6-338578 and iscaused through some other mechanism.

In FIG. 4, the operation condition giving acceptable etching rate ofsilicon dioxide distributes in the area showing that the flow rate ofnitrogen is far larger than that of water vapor in the mixed gas. It isknown that many excited nitrogen molecules with long life-time at ameta-stable energy state of which potential energy is about 10 eV areproduced in plasma. The potential energy of these nitrogen molecules isenough to disassociate H₂O and NF₃. This suggests that the etchingspecies might be produced by another reaction such as that between H₂Oand NF₂ instead of the reaction between the hydrogen atom and NF₃. Infact, etching did not occur when N₂ and NF₃ were injected into thedownstream of a 100% H₂O plasma, then few exited nitrogen existed in thedownstream. Therefore, though the accurate mechanism is not clear, it isseen that the etching using the mixed gas of nitrogen and a little watervapor is mainly caused by the catalytic effect of nitrogen throughplasma not caused by the mechanism depending on the reaction betweenhydrogen atom and NF₃ and described in the official patent report KOKAIH6-338578.

If the catalytic effect of nitrogen at meta-stable state makes itpossible to use H₂O as the source of the hydrogen atom, other inertgases having long life meta-stable energy state, such as Helium, Neon,Argon, are also available. Actually, the silicon dioxide etchingphenomena has been confirmed in the treatment that NF₃ was injected intothe downstream of a plasma generated using a gas composed by 90% Argonand 10% H₂O as a plasma source gas, though its etching rate wasrelatively smaller than that using the mixed gas of nitrogen and a fewpercent of water vapor.

This effect suggests that NH₃ can be used for this process instead ofH₂O. NH3 also has risk of explosion. In this process, however, theconcentration of the catalytic species can be much larger than that ofprocess species such as water vapor. Namely, for example, nitrogencontaining NH₃ whose concentration is lower than its explosion limit.Actually, as shown in FIG. 6, lower concentration of NH₃ in nitrogenbrought higher etching rate. The explosion limit of NH₃ in atmosphere isbased predominantly on concentration. Taking gas pressure in the vacuumpump and at the exhaust port into consideration, it is preferable to useNH₃ at lower concentration than the explosion limit at atmosphere.

FIG. 2 shows the equipment for this invention. As shown is a plasmadischarge section 11 for a plasma source gas made of such as quartz oralumina. Reference numeral 12 is the Gas-A supply unit and numeral 13 isthe Gas-B supply unit both of which are structured with mass flowcontroller, valve and filter. Mixed Gas-C, which is mixed with Gas-Aprovided Gas-A supply unit 12 and Gas-B provided Gas-B supply unit 13,is introduced into plasma discharge room 11 through the fitting-14.Mixed Gas-C introduced into the plasma discharge room-11 is dischargedinto plasma by microwave, which is supplied to microwave cavity-17through microwave guide-16 from microwave generator-15. The nozzle 18 toadd another gas is set at a suitable point in the downstream region ofthe plasma discharge area in the plasma discharge room 11. Gas-D isinjected into plasma downstream through the fitting-20 from Gas-Dsupplier unit-19. Gas-D supply unit is structured with mass flowcontroller, valve and filter. Plasma discharge room 11 is connected withtreatment room 22 with O-ring 21. The surface of object 23 which placedinside of the treatment room 22, is processed by the gas which isprepared by discharged Gas-C and injected Gas-D. The object 23 is placedon stage 24 and Si-C heating unit 25 is instrumented at upper section ofstage 24 in order to heat up the object 23. The treatment room 22 hasvacuum exhaust port 26 and connected to the rotary vacuum pump, which isnot showed in this schematic. The treatment room 22 also has thematerial transport port 27 in order to load and unload the object. Innerwall part 28 can be set inside of treatment room 22 in order to protectthe wall side of the treatment room or any other reason.

EXAMPLES 1. First Example

FIG. 5 shows the dependence of etching depth of SiO₂ on the mixing ratioof water-vapor and nitrogen in the surface treatment using the equipmentshown in FIG. 2. In this treatment, NF₃ of 100 sccm was injected intothe downstream of N₂+H₂O plasmas discharged by 2.45 GHz microwave of 500W and 6 inch silicon wafers covered by silicon dioxide as etching samplewere placed in the downstream of the NF₃ injected point. The maximumetching rate was obtained in the treatment with 5% water vapor but noetching occurred in the treatment with higher water vapor mixing ratiothan 25%.

In addition, native oxide removal was confirmed by the result that thehydrophilic surface of a 6 inch Si wafer covered by native oxide wasturned to hydrophobic after 3 minutes of downstream treatment. Thenmicrowave power was 500 W, pressure was 2.0 Torr, flow rate of NF₃ was100 sccm, and flow rate of water vapor and nitrogen was 10 sccm and 190sccm.

2. Second Example

FIG. 6 shows dependence of etching depth of SiO₂ on the mixing ratio ofwater vapor and nitrogen in the surface treatment using the equipmentshown in FIG. 2, for example. In this treatment, NF₃ of 100 sccm wasinjected into the downstream region of N₂+NH₃ plasmas discharged by 2.45GHz microwave of 500 W and 6 inch silicon wafers covered by silicondioxide as etching sample were placed in the downstream of the NF₃injected point. Nitrogen gas containing lower concentration of NH₃ thana selected percentage based upon FIG. 6. served good etching result.

Additionally, native oxide removal was also confirmed by the result thatthe hydrophilic surface of a 6-inch silicon wafer covered by nativeoxide was turned to hydrophobic after 3-min downstream treatment. Thenmicrowave power was 500 W, pressure was 4.0 Torr, and flow rates of NF₃,NH₃, and nitrogen are shown in FIG. 6.

3. Third Example

Silicon substrate placed on the treatment heat stage in the equipmentshown in FIG. 2 is processed in downstream of a nitrogen plasma with 5%of water-vapor (10 sccm). Flow rate of nitrogen containing 5% of watervapor was total 200 sccm. Applied microwave (2.45 GHz) was 500 W togenerate plasma. In this treatment, silane gas of 5 sccm was injected atthe downstream. Substrate temperature was kept at 450 degree C. duringprocessing and treatment time was 1 hour under pressure at 2 Torr. Bythe processing, certain deposited film was formed on the silicon wafersurface and the surface of the film was hydrophilic.

After dipping this sample into 5% of HF diluted solution for 1 minute,the silicon surface became the hydrophobic. This indicates that thedeposited material must be some kind of silicon-oxide-material.

4. Fourth Example

Silicon substrate placed on the treatment heat stage in the equipmentshown in FIG. 2 is processed in downstream of a nitrogen plasma with 5%of water-vapor (10 sccm). Flow rate of nitrogen containing 5% of watervapor was total 200 sccm. Applied microwave (2.45 GHz) was 500 W togenerate plasma. In this treatment, ethyl alcohol of 5 sccm was injectedat the downstream. Substrate temperature was kept at 600 degree C.during processing and treatment time was 3 hr. By this treatment,silicon wafer surface was discolored by a deposited film. In order toprobe what this deposited material was, the sample was treated withplasma ashing system.

FIG. 7 shows the barrel type plasma ashing system is used to processwafer 35 on the wafer carrier 34 by oxygen plasma which is generatedinside of quartz reaction tube 31 induced oxygen and supplied RF powerinto the electrode 32 a and 32 b from RF generator 33. Wafer 35 is loadand unload at the part of open side of quarts tube 31, and use cover 36at the processing time to cover quartz open side. Aluminum etch tunnel37 is also available. Previous processed Si wafer with a deposition filmwas processed with this type of oxygen ashing system under conditions ofoxygen gas flow 500 sccm, 1 Torr and 300 watt RF power for 30 minutes.This processing stripped previously observed deposited material. This isthe indication that previous deposit material should be some type ofcarbon content material such as amorphous carbon or diamond like carbon.The result shows that this method can be used to produce carboncomposite material film include diamond.

As above description, surface treatment in which atomic hydrogen was theone of the necessary species is realized by the use of a gas mixed a gascontaining essentially water vapor and a gas containing nitrogen, helium(He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and/or radon (Rn),through the catalytic effect induced on nitrogen, helium (He), neon(Ne), argon (Ar), krypton (Kr), xenon (Xe) and/or radon (Rn) by theplasma, though water vapor was used for the source of atomic hydrogen.Accordingly, this invention makes it possible to inexpensively andsafely use the atomic hydrogen surface treatment without special safetyprotection system and circumstance.

For example, in comparison with conventional water vapor added hydrogenplasma system, this technology can substantially eliminate the load lockmodule, object transfer system specialized to load lock environment,pumping package applicable to hydrogen evacuation, exhaust gas treatmentsystem, safety and alert system, and other hardware. Thus, thisinvention provides the cost reduction of this system over 10,000,000 yenper unit (in 1998) depending on the purpose of system and the conditionof operation.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A method of treating an object, the method comprising: positioning the object to be treated using an etching process in a process chamber; generating a plasma from a gas mixture comprising a first gas, the first gas being selected from the group consisting of a nitrogen bearing compound and an element in group 18 of the atomic periodic table, and a second gas, comprising an NH₃ bearing compound; passing the plasma along a conduit after the plasma has been generated; injecting a third gas into the conduit to form a mixture species from the plasma and the third gas; and passing the mixture species from the conduit into the process chamber away from where the plasma has been generated so as to etch the object in the process chamber with the mixture species, whereupon the object is substantially free from physical surface damage; wherein the NH₃ is provided at a concentration below an explosion limit defined at 1 atmosphere pressure.
 2. The method of claim 1 wherein said object is a semiconductor wafer having a layer of oxide and the method comprises substantially maintaining the layer of oxide on the semiconductor wafer.
 3. The method of claim 1 wherein said mixture species comprises atomic hydrogen.
 4. The method of claim 1 wherein said method occurs in an apparatus not having a load lock module.
 5. The method of claim 1 wherein the gas comprising an element in group 18 of the atomic periodic table is selected from the group consisting of helium, neon, argon, krypton, xenon, and radon.
 6. The method of claim 1 wherein the compound comprising a nitrogen bearing compound is selected from the group consisting of N₂ and NF₃.
 7. The method of claim 1 wherein said plasma is generated by a microwave source.
 8. The method of claim 1 wherein said plasma is generated in a microwave cavity.
 9. The method of claim 1 which further comprises increasing a temperature of the mixture species to up to 500 degrees Celsius.
 10. A method of treating an object, the method comprising: positioning the object to be treated including etching in a treatment room; generating a plasma in a plasma discharge room from a gas A the gas A comprising a nitrogen bearing compound, and a gas-B, the gas B comprising NH₃; passing the plasma from the plasma discharge room to the treatment room; injecting a gas D into the plasma at a location between the plasma discharge room and the treatment room through a nozzle so as to form a mixture of said plasma and said gas D; and introducing the mixture into the treatment room so as to etch the object in the treatment room with a mixture species generated from the plasma and said gas D, whereupon the object is substantially free from physical surface damage; wherein the NH₃ is provided at a concentration below an explosion limit defined at 1 atmosphere pressure.
 11. The method of claim 10 wherein said gas D is selected from the group consisting of silane, alcohol, and NF₃.
 12. The method of claim 10 wherein said mixture species comprises atomic hydrogen.
 13. The method of claim 10 wherein said method occurs in an apparatus not having a load lock module.
 14. The method of claim 10 wherein said nitrogen bearing compound is selected from the group consisting of N₂ and NF₃.
 15. The method of claim 10 wherein said plasma is generated by a microwave source.
 16. The method of claim 10 wherein said plasma is generated in a microwave cavity.
 17. The method of claim 10 further comprising increasing a temperature of the mixture species to up to 500 degrees Celsius.
 18. A method of treating an object, the method comprising: positioning the object to be treated using an etching process in a process chamber, the object including an overlying thin layer of silicon dioxide overlying a surface on the object; generating a plasma from a gas mixture comprising a first gas, the first gas being selected from the group consisting of a nitrogen bearing compound and at least an element in group 18 of the atomic periodic table, and a second gas, the second gas comprising an NH₃ bearing compound; passing the plasma along a conduit after the plasma has been generated; injecting a third gas into the conduit to form a mixture species from the plasma and the third gas; passing the mixture species from the conduit into the process chamber away from where the plasma has been generated; applying atomic hydrogen in the mixture species to the surface of the object to process the surface of the object; removing the thin surface of silicon dioxide from the surface of the object with the mixture species including the atomic hydrogen, whereupon the surface of the object is substantially free from physical surface damage; wherein the NH₃ is provided at a concentration below an explosion limit defined at 1 atmosphere pressure.
 19. The method of claim 18 wherein said method occurs in an apparatus not having a load lock module.
 20. The method of claim 18 wherein the gas comprising an element in group 18 of the atomic periodic table is selected from the group consisting of helium, neon, argon, krypton, xenon, and radon.
 21. The method of claim 18 wherein the compound comprising a nitrogen bearing compound is selected from the group consisting of N₂ and NF₃.
 22. The method of claim 18 wherein said plasma is generated by a microwave source.
 23. The method of claim 18 wherein said plasma is generated in a microwave cavity.
 24. The method of claim 18 which further comprises increasing a temperature of the mixture species to up to 500 degrees Celsius. 